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Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
Lecture2_Networking_..
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Transcript

  • 1. ITP 457 Network Security Computer Networks
  • 2. Overview
    • Brief Introduction to Computers and Computer Components
    • What is a network?
    • Introduction to Physical Networks
    • LANs, WANs, and MANs
    • Logical Network Topologies
  • 3. Introduction to Computers
    • Computers
      • Made up of hardware and software
      • Software cannot run by itself, and without software, your computer is an expensive paperweight
    • Main Components
      • CPU (Central Processing Unit) – does the math that is necessary for computer use
      • Memory
        • RAM (Random Access Memory) – temporary memory, very fast, not very big
        • Secondary Storage – Hard Disks, Optical Media; large and slow
      • Network Interface Cards – allow computers to communicate with one another
      • Additional Add-In Cards include Sound, Video, SCSI, Firewire, etc.
  • 4. Operating Systems
    • Manages hardware and software so the user does not have to micro-manage
    • Microsoft
      • Windows 95/98/ME
        • Very limited networking capabilities
        • Blue Screen of Death!!!
        • Microsoft has completely abandoned this Operating System. We will not cover these OSes in this class
      • Windows NT/2000/XP/2003
        • Built on the NT kernel, which is a much more stable and network savvy kernel
        • Security is an issue, due to holes in the O.S.
        • We will cover these operating systems extensively
  • 5. Unix
    • Server-workstation operating system meant to be portable, multi-tasking, multi-user, & time sharing
    • Originally written in the 70s
      • Extremely popular, even today as Solaris 10
      • Was the primary reason that the programming language C grew to be the de-facto language
    • We will not cover Unix in this class
  • 6. Linux
    • Uses the Linux kernel, with a bunch of other stuff
    • Its open-source, meaning its free to use and develop
    • Most people download a distribution, which is a package of the Linux kernel with a bunch of other useful modules
      • You pay for documentation, proprietary modules, and support
    • Is becoming very popular, due to the fact that it is free, reliable, and the linux community is very helpful in forums and IRC
    • We will spend a few weeks on Linux, due to its popularity as a workstation and server operating system
  • 7. Mac OS
    • One of the first graphical user interfaces
      • Introduced in 1984
    • Original Mac OS (1984 – 2001)
      • Versions 6 – 9
      • No command line; single tasking or very limited multitasking
      • Horrible memory management – user had to manually allocate memory
    • OS X
      • Complete rewrite using the Mach Kernel and the Free BSD implementation of Unix
      • Has software emulation for older software
      • Now runs on Intel based processors
    • We will not cover too much of Mac based security, but the same principles for Linux security can be applied to Macs.
  • 8. Computer Networks
    • Minimum: Two or more connected computers
    • A good computer network consists of the following
      • All hosts must use the same standard method for sending and receiving data
      • Information must be delivered without any corruption
      • There must be a way of acknowledging that the data has reached it’s destination
      • Nodes must be able to determine the source of the communication
      • The network should be scalable
      • Nodes must be able to identify other nodes
      • The network should run without the need for user micro-management
  • 9. Computer Network Components
    • Two main parts to the network
      • Physical Network
        • Physical connection between devices or nodes
        • Hardware
        • Wiring
        • Wireless devices as well, but they are a little bit more complicated to understand
      • Logical Network
        • Lays out the roles and routes for data transmission
        • Dependent on the Protocol used for networking
        • Software
  • 10. Physical Network
    • Wires, cables, printers, hubs, switches, computers, servers, etc.
    • Computers use Network Interface Cards (NICs) to interact with the network
    • Network Topology
      • Physical layout of components on the network
      • Star, Ring, and Bus are the most common topologies
        • Mesh is becoming more prevalent, especially with wireless
  • 11. Bus Topology
    • A long line with computers connected
      • Called “taps” in the line
    • Components on the computer motherboard are connected using a bus
    • 10Base2, 10Base5 use bus topologies
    • Advantages:
      • Simple
      • Cheap
      • Quick Set-up
    • Disadvantages:
      • Difficult to troubleshoot
      • One break in the line causes the whole network to go down!!!
      • Performance is directly proportional to the number of nodes on the line
      • Very low security – all computers on the line can see the data
      • Collision!!!
        • Two computers trying to send information at the same time
        • Carrier Sense Multiple Access fixes this somewhat
  • 12. Ring Topology
    • Every node has two connections, to create a closed network
    • Token Ring and FDDI (Fiber Distributed Data Interface) use Ring Topologies
    • Advantages:
      • Additional nodes do not directly impact performance (with a good protocol)
      • No packet collision
    • Disadvantages:
      • Slow – data must pass through multiple nodes to reach destination
      • Any node failure causes the ring to die
      • To add a node, you must shut down the network
      • All systems must be on for the ring to work properly
      • Complete dependence on one cable – no redunancy
  • 13. Star Topology
    • The most common topology for home and business networks
    • Nodes have a connection to a central hub
    • The hub can be connected to other hubs to create intricate diagrams
    • 10BaseT, 100BaseT
    • Advantages:
      • Good performance – limits the number of nodes to travel through
      • Easy to set-up and expand
      • A non-centralized failure will not bring down the network
    • Disadvantages:
      • Most expensive topology – requires the most cabling and most hardware
  • 14. Mesh Topology
    • Think of a combination of a star and ring topology
    • Multiple ways for data to travel from source to destination
    • Wireless Ad-Hoc networks are mesh networks
      • Wireless infrastructure (wireless access points and routers), are more of a star topology
    • Advantages:
      • Extremely reliable & self healing
      • Easily scalable
    • Disadvantages:
      • You never know exactly how the data is going to travel
      • The data may not flow in the most optimized manner
        • In order to find the most optimal route, all routes must be tested
      • Virus propagation is a HUGE issue
  • 15. Network Sizes
    • Completely arbitrary – no set definition of each
    • LAN – Local Area Network
      • All computers are networked together
      • Only occupies one “site”
      • Typically high speed (100 Mbits/sec or 1 Gbit/sec)
    • WAN – Wide Area Network
      • Geographically separated LANs connected with routers and high-speed interconnections
      • Typically connected with telephone, T1 or T3 lines, or Cable/DSL lines
    • MAN – Metropolitan Area Network
      • Larger number of WAN or LANs connected typically using wireless or fiber lines
    • Internet
      • Either a WAN or a MAN, depending on how you define it 
  • 16. Logical Topology
    • While the physical topology defines how the nodes are connected, the logical topology defines how the data is to be sent and how the network behaves from a software standpoint
    • Ethernet
    • Token Ring
    • FDDI
  • 17. Ethernet
    • Most common logical topology
    • Logical common bus topology
    • Single bus to which all communication occurs
    • Uses CSMA/CD – Carrier Sense Multiple Access/Collision Detection
      • All computers share a single network segment
      • Every computer listens on the network segment
      • If no other computer is transmitting at that time, then the computer can transmit data
      • If two computers send data at the same time, then a collision occurs. Both computers sense the conflict, and stop sending. They wait a “random” amount of time (in nanoseconds), then retransmits the data.
  • 18. Ethernet Continued
    • Is classified as IEEE 802.3 & 802.3u
      • 10BASE-2: coaxial networking – dead
      • 10BASE-5: thicknet – dead
      • 10BASE-T: 2 of 4 pairs of unshielded twisted pair wire called CAT5 cabling; speed of up to 10 Mbits/sec; dead
      • 100BASE-TX: fast ethernet; 2 of 4 pairs of unshielded twisted pair wire; speed of up to 100 Mbits/sec; seen everywhere
      • 100BASE-FX and 100BASE-FL – fast ethernet on optical fibers; speed of up to 100 Mbits/sec; more expensive than 100BASE-T; not used a whole lot anymore
      • 1000BASE-T: uses all 4 pairs of CAT5e or CAT6 cabling; speed of up to 1000 Mbits/sec
  • 19. Token Ring
    • Problem with CSMA/CD: Lots of computers on a network segment can cause starvation – computer may never get to transmit data
    • IEEE 802.5 – Token Ring
      • A special packet called a Token packet is passed around the ring
      • A computer can only transmit data when the computer has the token
      • When the computer is done transmitting, it releases the token
    • FDDI – Fiber-Distributed Data Interface
      • Uses fiber optic lines instead of a copper wire
      • Can support thousands of users
      • Speed of up to 100 Mbits/sec
      • Has backup-ring in case of primary ring failure
      • Gigabit ethernet has made FDDI obsolete

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